The starting of pumps or turbopumps functioning as pumps must generally be carried out with drowned wheels to avoid a fierce intake of current at the moment the pump is primed, which causes surges in the electrical power distribution system. For example, in the case of starting turbopumps functioning as pumps, and when, as is the case for the pumps of the invention, a turbopump with fixed distributor is involved, the conventional starting sequence, with the guard valve closed, consists in starting the pump, either by means of an auxiliary synchronous motor, or by means of its synchronous motor then operating, thanks to special equipment such as "dampers", or to an oversizing of armature windings, as an asynchronous motor. The speed is then progressively increased until it reaches the synchronous speed. Then the synchronous motor is coupled and the guard valve progressively opened until nominal flow is obtained. The zero-flow power supplied near synchronous speed, called "bubbling power", is often a nonnegligible fraction of the nominal power, and can reach 70% of the latter. From this results on the one hand a heating of the zero-flow water which, through a differential expansion of certain turbine-parts, among fixed parts and movable parts, can lead to damage to some of these parts, and on the other hand a need for overdesigning of the motor used for starting, whether this is an auxiliary motor, the principal turbopump motor or the principal asynchronous motor of the pump, if a conventional pump is involved. Now, it has been established that the Power-Flow characteristic at nominal speed of a pump or turbopump functioning as a pump very often passes through a minimum situated between the zero-flow point and the nominal-flow point. This minimum, generally to be found at a flow of 10 to 20% of the nominal flow, is generally about 15% less than bubbling power at zero flow.